The invention relates generally to quartz crystal resonators utilized for frequency controlled apparatus and the like and more particularly to a technique for accurately correcting the angle of cut of quartz crystal resonator blanks or plates.
It is well known that quartz crystal plates utilized for frequency control apparatus normally cannot be cut with sufficient accuracy where high precision applications are intended. Thus, following the initial cutting operation, the crystal blanks must have their orientation angles or angles of cut corrected prior to their installation in the respective equipment with which they are to be utilized.
In U.S. Pat. No. 3,803,774, entitled, "Technique For Correcting the Crystallo-Graphic Orientation Angle of Crystals by the Formation of Mesas and Double Face Lapping", issued to A. J. Miller on Apr. 16, 1974, there is disclosed a technique for correcting the angles of cut of quartz plates which involves first the formation of mesas by various methods such as etching, machining or mounting a chip on the surfaces of the plate, followed by a double-face lapping operation until the mesas are removed, at which point the angle of cut has been changed by the desired amount and the lapped upper and lower surfaces of the plate are substantially parallel.
An inherent problem, however, arises in the masking of quartz plates during etching due to the fact that the masking material is attacked by the etchant and due to the complexity of the method of applying and removing the masking materials themselves. Various tapes, photo-resists and solder-resists have been utilized, but to date none has proved to be satisfactory . Chemical and ion etching has been suggested in U.S. Pat. No. 3,694,677, entitled, "VHF-UHF Piezoelectric Resonators", issued to G. K. Guttwein, et al. on Sept. 26, 1972. In U.S. Pat. No. 3,489,564, entitled, "Photolytic Etching of Silicon Dioxide", issued to D. L. Schaefer, on Jan. 13, 1970, there is disclosed a process whereby the etching of a predetermined pattern for decorative and optical purposes is achieved by exposing the surface of the body to be etched with radiation which has been previously treated by a photolytically decomposable liquid.
It is an object of the present invention, therefore, to provide an improved technique for correcting the angle of cut of a quartz resonator blank.
It is another object of the present invention to provide a technique for correcting the angle of cut of a quartz resonator plate or blank which substantially eliminates the need for the formation of mesas and subsequent lapping operations.
It is a further object of the invention to provide a photolytic etching technique for correcting the angle of cut of a quartz crystal resonator blank.
And it is yet another object of the invention to provide an automated photolytic etching correction process for correcting the angle of cut of a quartz resonator blank or plate.